Shiva Purana
अभ्यर्च्य गन्धपुष्पाद्यैः प्रणवेन च सप्तधा । अभिमंत्र्य ततस्तस्मिन्धेनुमुद्रां प्रदर्शयेत् ॥ ३ ॥
Then worship the Lord with fragrant flowers and other oṁkāras in seven parts. After chanting the mantra one should then present the cow mudra to the deity.
english translation
abhyarcya gandhapuSpAdyaiH praNavena ca saptadhA । abhimaMtrya tatastasmindhenumudrAM pradarzayet ॥ 3 ॥
hk transliteration by Sanscript